In many cultures, the groom historically often kidnapped the bride, and the groom’s friends would help him, leading to the modern-day groomsmen. At the alter, the groom always stood on the bride’s right side so his right hand—or his sword hand—would be free to fight/defend a jealous rival.

Bride’s Book of Etiquette. 2002. New York, NY: Perigee Books./randomfacts.com